Identify differences between (consequences for) only children and others to see whether such differences can be accounted for by the mediating or control variables. If there are multiple differences, their relationships will be examined to simplify and clarify them, e.g., by treating some consequences as contributing to others. Analysis will be undertaken of Cycles II and III of the National Health Examination Survey Data on the only child compared with children in multiple-children families. Longitudinal analysis will draw upon the one-third of the sample who were in both cycles.